Looking for materials to supplement your Singapore Math® curriculum? Here are some direct links:
Placement tests on Singapore Math.com
Challenging Word Problems Series – What’s great about this series is that it includes examples & on-grade level problems AND examples & at a challenge level
Extra Practice U.S. Edition books
i-Excel Heuristic and Model Approach books
These are great, but out of print. Try eBay. They are replaced by:
Process Skills in Prob Solving
Visible Thinking in Mathematics
Math Works Foundations series for 5th & 6th grades